The publication “802.16™ IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems”, published on Oct. 1, 2004 and its amendments e.g. IEEE 802.16e-2005 will be referred herein each and collectively as the “IEEE 802.16 publication”. The disclosure of this reference is hereby incorporated herein by reference.
Bandwidth requesting/allocation mechanism specified in the IEEE 802.16 publication is optimized for the situation when data transmission demand appears/changes in a completely random manner. To keep the system latency reasonably small, a mechanism has been suggested, based on the usage of “MAP messages”. This mechanism allows that within a short time interval (called “frame”) the Base Station (“BS”) can make a decision on allocating certain amount of bandwidth within the frame for service flows which initiated the data transmission demand.
Consequently, such a scheme requires that a MAP message be transmitted every frame. As MAP message is of a broadcast type of transmission, it will typically be transmitted over a control channel at the lowest possible rate so that all terminals in the cell will be capable of receiving it. Therefore, it appears that the MAP message is one of major elements of the MAC overhead. While MAP message for downlink (referred to in the IEEE 802.16 publication as “DL-MAP”) typically allows for integrating transmissions directed to several terminals in a single transmission burst represented by a single element of DL-MAP, MAP message for uplink (UL-MAP) should explicitly specify transmission region for every terminal, so that the length of a UL-MAP is the most important element of the overhead. The length of a UL-MAP is roughly proportional to the number of service flows for which transmission slots are allocated in a single frame. This number is especially large in case where the transmissions from individual terminals are relatively small. One of the most important scenarios in which this problem can be demonstrated is in the case where there are many voice calls i.e. when many of terminals have VoIP packets ready for transmission.